Ocular aging

two common biochemical degradation reactions in the eye

- Apoptosis: programmed death by a series of biochemical cascades

- Necrosis: cell die by loss of membrane

steps involved in apoptotic cascade

a death signal (FasL) binds to death receptor (Fas)

-> initiates series of amplification reactions to activate caspase enzymes

-> proteolytic enzymes bring about hydrolysis of key cell proteins and degradation of DNA

two proteins regulating apoptosis and their role?

Bax (promotes apoptosis)

Bcl (inhibits apoptosis)

major change occurring during vitreal liquefaction and what are its

consequences to the retina?

liquid volume increases and vitreous gel decreases.

destabilizes retina and leads to retinal detachment

Name the collagens contributing to the gel property of vitreous

Collagen II and IX

What are the roles of type IX collagen vitreous?

GAG component of IX collagen acts as molecular spring between collagen fibers.

role of Opticin in vitreous

a protein that attaches to collagen and prevents the fibers from aggregating

three immediate effects of alkali burns in the cornea?

- cellular destruction

- distortion and lysis of collagen fibers

- removal of GAGs from proteoglycan protein cores

consequences of alkali burn on the cornea?

varying degrees of cloudiness and opacification of cornea.

- later invasion of PMNs

How do PMNs enter cornea following alkali burn injury?

due to chemotactic attraction of collagen peptide remnants

What are the changes caused by MMPs in the cornea following alkali burn injury?

MMPs in cornea bring further destruction of collagen and lead to perforation of cornea upon development of ulceration.